CCL2 and COVID-19: MC activation also leads to de novo production of cytokines and lipid mediators, including TNF, IL-6, CCL2, CCL3, prostaglandin D2 and E2, and leukotriene B4 and C4 (14, 15), many of which are now known to be associated with the cytokine storm observed in COVID-19 (5–7, 16).